In parking brake systems for motor vehicles having foot operated parking brake controls, it is possible to impose a load upon the components in the wheel brake that exceeds a desirable limit. According to the present invention, a means is provided for limiting the forces exerted upon a cable actuated wheel brake.
A brake system in accordance with this invention includes a parking brake control pedal to which an actuating cable is connected. A wheel brake has a brake cable connected thereto. The two cables are connected to an intermediate lever. The intermediate lever in turn is supported on a support lever or movable fulcrum member. The support lever is displaceable between a normally stationary support position and a force limiting position. A coil spring urges the support lever to its normal position.
The application of a force on the parking brake pedal by the vehicle operator will cause the actuating cable to displace the intermediate lever from a brake released position to a brake applied position. Displacement of the intermediate lever, in turn, will cause the cable running to the wheel brake to be tensioned and the brake to be applied. When the tensions in the two cables reach predetermined maximums, the force imposed upon the support lever by the intermediate lever will cause the support lever to overcome the force of its retaining spring and to pivot from its support position to its force limiting position. Thus, with this double lever construction, tensioning of the actuating cable by the parking brake pedal by an amount that exceeds a predetermined maximum will cause displacement of the support lever rather than additional loading of the wheel brake cable. Such action will prevent an excessive build up of forces in the wheel brake.